Parental ethnotheories, or parents’ beliefs about their children’s development, provide a framework for cultural transmission of values and behaviors. In this study we aimed to understand Guatemalan mothers’ beliefs about children’s learning, what is “good” and “bad” behavior, and the desired qualities of grown-up children. Twenty-two low-income mothers (ages 20 through 70) were interviewed about their beliefs with respect to learning and desired qualities of children. Mothers reported that good children are obedient and respectful, behaviors that they learn from their parents. Good girls help with housework and boys study hard. Bad children are disobedient and disrespectful, behaviors that they learn from their friends or “on the street.” Grown-up children were expected to be hard-working and respectful. It will be important to understand how these parental beliefs are instantiated in mothers’ parenting behavior in the changing diverse context of Guatemalan society.